This randomized, phase 2, 3-arm study was designed to compare docetaxel + carboplatin + trastuzumab + pertuzumab (TCbHP), TCbHP followed by T-DM1+P, and T-DM1+P for treating HER2+ primary breast cancer patients as a Japan Breast Cancer Research Group (JBCRG) association study-20, Neopeaks. Here, ERBB2 is linked to breast cancer.